82 PALEONTOLOGY OF NEW YORK. 



directed slightly forward, depressed. Umbonal region moderately prominent, 

 subtending an angle a little less than 90°. 



Ears triangular, Hat, extremities acute. Anterior ear smaller, defined l>y 

 a sulcus; margin nearly straight. Posterior ear with the margin concave, 

 extremity acuminate ; having no strong radiating striae. 



Test, as indicated in an exfoliated specimen, marked by a few fine radiating 

 stria 1 , with wider interspaces which are marked by finer radii. Anterior 

 ear showing the same characters. Posterior ear free from rays. Fine con- 

 centric striae cross the rajs, and stronger concentric wrinkles interrupt them 

 and produce a slight crennlation of the radii. 



The specimen is 10.5 mm. in length, 10 mm. in height, with hinge-line a 

 little more than 1 1 mm. 



This species resembles in form the young of Pterinopecten dignatus, hut differs 

 in the finer radiating lines on the body of the shell, the concave margin, and 

 absence of rays on the posterior ear. 



Formation and locality. In the black Marcellus shale at Cherry Valley, Otsego 

 county, N. Y. 



AVK TLorEOTEN (PtERINOPECTE.N ?) TEKMIXALIS. 

 PLATE I, FIG. 3. 



I'h riii, tpirti ii it rmiiidlis. EI all. Pal. N. V., vol. v, pt. 1. Plates and Explanations : PI. 1, fig. 3. Jan.. lss:i. 



Shell small, rhomboidal ; body of the shell obliquely ovate; length a little 

 greater than the height; margins regularly rounded, somewhat extended 

 behind. 



Left valve very convex. Right valve unknown. 



Hinge-line straight, central, equal to the length of the shell. 



Beak acute, prominent, directed a little forward, arching over the hinge- 

 line. Umbo elevated, subtending a right angle. 



Ears triangular; margins concave; extremities acute. Posterior ear larger, 

 undefined. Anterior ear limited bv a shallow sulcus. Byssal sinus moderate. 



